Large, utility-scale horizontal-axis wind turbine generators (HAWTs) typically comprise a set of rotor blades mounted to a supporting structure which usually takes the form of a tubular tower. In such HAWTs, the generating components including the generator, gearbox, drive train and brake assembly are located at the top of a tower in a nacelle behind the hub of the rotor blades.
It is known to install lifting apparatus within a nacelle in order to help personnel install heavy components. For example, WO2012/107049A1 describes a boom crane that is mounted within a nacelle of a HAWT, wherein the boom is movable in elevation and in azimuth in relation to the nacelle. In a stowed position, the boom crane lies inside the nacelle and is covered by a roof. However, the boom crane can be moved to a deployed condition in which the boom is able to reach beyond the roof level to access other parts of the nacelle. For instance, the boom is able to reach a helihoist platform to transfer loads from the platform into the body of the nacelle, but is also able to reach beyond the side of the nacelle to hoist loads from the surface if necessary.
The almost continuous operation of wind turbines generates vibrations. It is believed that these vibrations can lead to dynamic loads such as boom oscillations which may cause wear or which may otherwise adversely affect the long-term reliability of lifting apparatus housed within the nacelle. It is against this background that the invention has been devised.